1.) Field of the Invention
The present invention relates generally to the manufacture of vacuum-deposited thin-film structures and more particularly to the manufacture of thin-film magnetoresistive (MR) read sensors for magnetic information storage files.
2.) Description of the Prior Art
Magnetic head disk drive systems have been widely accepted in the computer industry as a cost-effective form of data storage. In a magnetic disk drive system a magnetic recording medium, in the form of a disk, rotates at high speed. A magnetic read/write transducer, referred to as a magnetic head, is attached to or formed integrally with a "slider". The slider flies over the rotating disk surface, in order to access the entire disk surface for information storage and retrieval. The slider and its integrally formed transducer are produced en mass in the form of a wafer. The bottom surface of the slider which is defined by cutting and grinding after the wafer process is called the airbearing surface (ABS).
A state-of-art magnetic head includes an inductive write-element and a magnetoresistive (MR) read-element. A MR read-element is also abbreviated as a MR-element element. It further consists of a MR-stripe, whose resistance varies with the magnetic flux from the medium, and two magnetic shields, which help the MR-stripe to "focus-on" a narrow stripe (approximately 100 nm wide) of the medium.
There are presently two types of MR-stripe, amorphous (AMR) and giant (GMR). Regardless of the type, a MR-stripe is located between two magnetic shields. Insulation is added between the MR-stripe and each shield to avoid shunting. In pursuit of high spatial resolution, the shield-to-shield spacing (which is also called the read-gap width) is presently as low as 150 nm. Less the thickness of MR-stripe, insulation on each side of the MR-stripe is as thin as 20 nm. Each insulation typically consists of a dielectric film such as aluminum oxide or silicon oxide. It is very vulnerable to accidental dielectric breakdown, during the manufacture and usage. The dielectric breakdown, commonly called arcing, causes shunting. It may also blow up the MR-stripe.
While it is difficult to prevent arcing through the insulation, it also takes much effort to create a desired electrical connection through the same insulation. Conventionally a layer of photoresist is applied on top of the insulation, then exposed through a dedicated mask. The photoresist and the insulation are chemically etched away in areas defined by the exposure, creating via-holes. The remaining photoresist is stripped away. Finally conductive material is deposited through the via-holes, establishing desired electrical connection. This process is viable, but nonetheless costs money and time.
Very often an electrical connection through the dielectric film does not require a precisely controlled conductivity. For example, it is desirable to connect the magnetic shields and the write-core to the ground-lead of the MR-stripe. The connection helps to prevent unintentional dielectric breakdown. It also helps to reduce the readback noise in an operating disk drive. See Schwarz and Keel (U.S. Pat. No. 4,800,454), Sato el al. (U.S. Pat. No. 4,802,043), Shibata and Suyama (U.S. Pat. No. 5,247,413), Shibata el al. (U.S. Pat. No. 5,272,582), and Denison el al. (U.S. Pat. No. 5,539,598). Electrical connections caused by arcing provide adequate conductivity for the above application. However such connections are never relied upon because arcing was considered uncontrollable.
The difficulty in preventing and utilizing arcing demonstrates the need for better understanding and control of arcing in wafer process. The present invention describes novel structures and methods useful for controlling arcing in wafer process.